The investigator proposes to test a new alternative hypothesis about the role of the cerebellum in mammalian brain function by combining neuroimaging studies in humans and multi-site electrophysiological studies in behaving rats. While a century of neurology and neurophysiology data have been interpreted to indicate that the cerebellum is devoted to fine movement control, recent neuroimaging results suggest that cerebellar function may be more complex than simple motor control. The new hypotheses about cerebellar function elicited by these findings are based only on neuroimaging data and are not connected to cerebellar neurobiology or cerebral circuitry. By contrast, the projects proposed in this grant are intended to establish connections between different physiological levels in the context of investigating a new hypothesis of cerebellar function derived from electrophysiological studies. This theory proposes that the known influence of the cerebellum on the motor system is to subserve the acquisition of sensory data, not the smooth or coordinated performance of movements in general. If so, it is likely that the cerebellum performs a similar role in data acquisition for a variety of sensory systems because the cerebellum has a uniform micro-structure, receives a great variety of its sensory inputs, and has reciprocal projections with much of the cerebral cortex. The results of investigating this novel hypothesis will have significant impact on basic neuroscience and clinical medicine. Advances in rigorously connecting neurophysiological and neuroimaging models should make important contributions to basic theory. Each specific aim of the project is focused on a specific implication of the investigator's hypothesis while providing new fundamental knowledge. Neuroimaging (positron emission tomography, fMRl) will be used to study whether human cerebellum has greater representation for primary motor-tactile body structures than for more purely motoric body structures and whether it represents body surfaces in a fractured somatotopy. The investigator will use human neuroimaging and rat neurophysiology to examine whether cerebellar cortex is more engaged by the demand for quality sensory data acquisition and whether changes in activity in cerebellar cortex reflect activity in cerebral cortex. Finally, neuroimaging will be employed to study whether cerebellar cortex is engaged in comparable ways by the need for high quality visual or auditory data acquisition.